Au-TiO2模型催化剂表界面的原位电子显微学研究

Since the catalytic property of catalyst depends on its surface and interface structures, to explore the interaction between surface/interface of catalyst and external environments is of great importance to understand the catalytic mechanism. Due to its excellent catalytic performance in CO oxidation reaction, TiO2–supported Au (Au-TiO2) catalyst has drawn great attentions. In the past decades, tremendous advances have been made in this model catalytic reaction, however the underlying catalytic mechanism remains controversial. A critical issue is that both the Au-TiO2 interface interaction, and the interaction between Au-TiO2 surface/interface and external environment are poorly understood. Herein, through spherical aberration-corrected transmission electron microscopy, environmental transmission electron microscopy and atmospheric pressure gas holder, this project aims to investigate the interaction mechanism between external environments and different surface/interface structures of Au-TiO2. In addition, the fundamental catalytic mechanism will be explored under the real catalytic reaction environments, through simultaneously monitoring the catalytic performance and surface/interface structure, composition, valence state evolution of Au-TiO2 catalysts. It is anticipated this project will not only help in understanding catalytic mechanism at the atomic and molecular level, which provide valuable information for designing high-performance catalyst, but also pave the way for future in situ surface/interface studies of other catalyst systems.

催化剂的表界面与其催化性能密切相关，因此研究催化剂表界面与外场环境的相互作用，对理解催化机理至关重要。Au-TiO2负载型催化剂以其优异的催化CO氧化性能引起广泛关注，近三十年关于这一经典体系有大量成果发表，但学术界关于其催化机理还存在很多争议。一个关键的原因是对Au和TiO2载体之间的相互作用机制及Au-TiO2表界面与反应气体的相互作用机制的认知还不充分。本项目拟通过球差矫正透射电镜、环境透射电镜及刚刚兴起的大气压样品杆技术，从结构视角梳理Au-TiO2体系一系列复杂的表界面构型与外场环境的相互作用机制；并通过质谱系统在原位观察催化反应的同时检测催化性能，揭示真实反应条件下Au-TiO2表界面原子结构演变、化学成分及价态变化与催化性能之间的内在联系。本项目不仅有助从原子、分子水平理解催化机理，为设计优异的催化剂提供有价值的信息，也为其他复杂催化剂体系在真实反应环境下的原位研究提供借鉴。

在气氛环境下原位探索催化材料表界面的结构演变对于理解催化反应机制和设计高性能催化材料具有重要意义。本项目利用环境透射电镜等原位电子显微学技术，在原子尺度气氛环境下对Au-TiO2模型催化剂表界面结构的动态结构演变进行了系统研究。原位研究了TiO2 (001)表面在不同环境下的热稳定性规律，在透射电镜中实现了对TiO2 (001)表面活性位点上吸附和反应分子的成像，给出了其表面活性位点的原子级直接实验证据；原位揭示了Au-TiO2催化剂表界面原子结构与其金属-载体相互作用的联系，揭示了其晶面依赖的烧结行为；揭示了Au-TiO2催化剂气氛依赖的烧结机制；在催化CO氧化反应环境中原位揭示了Au-TiO2 (001)催化剂界面活性位点的可逆转动行为，并据此实现了在反应环境下对Au-TiO2界面活性位点的原子级别原位调控。